Engine and vehicle speed regulation systems typically include a servo mechanism for positioning the engine throttle in order to achieve a desired speed and a coupling mechanism connected between the servo mechanism and the throttle for selectively engaging and disengaging the control. When speed regulation is desired, the coupling mechanism is actuated to engage the control; when speed regulation is not desired or when a malfunction is detected, the coupling mechanism is actuated to disengage the control.
In one type of speed regulation system, a Bowden cable or the like is attached to the engine throttle, and is positioned by the output shaft of a rotary electric motor through two or more gear elements. When the gear elements are in meshing engagement, the motor is connected to position the throttle; when the gear elements are moved out of meshing engagement, the motor is disconnected from the throttle. An example of a speed regulation system of this type is shown in the U.S. Pat. No. 4,187,734 to Mann issued Feb. 12, 1980.
A manufacturing and assembly problem with regulating systems of the type described above, is that unless the various system components are precision formed, their cumulative tolerance variations result in some system-to-system differences of operation. Respecting the coupling mechanism, it is important to ensure that the gear elements properly mesh or unmesh when it is desired to engage or disengage the control. As a result, some calibration of the coupling mechanism is needed if it is decided to forgo the expense of precision formed components.